1. Field
The present invention relates to aircraft thrust reversers. More particularly, the invention relates to a locking mechanism for a pivot door of a thrust reverser.
2. Related Art
A thrust reverser is a part of an aircraft typically incorporated into a fan duct surrounding an engine to reverse the aircraft's thrust during landing. Pivot door type thrust reversers are commonly used on corporate or business jet applications, and are designed to pivot to an open position when deployed, creating a resistance opposing engine thrust. However, inadvertent pivot door deployment in flight can be catastrophic to the aircraft. Therefore, door locks for maintaining the pivot doors in a stowed position during flight are required. To meet regulatory requirements, each pivot door typically comprises or mates with three locks.
For example, as illustrated in FIGS. 1-3, a thrust reverser (A) may have an upper pivot door (B) and a lower pivot door (C). The upper pivot door (B) may have a first upper door hook (D) and a second upper door hook (E), and the lower pivot door (C) may have a first lower door hood (F) and a second lower door hook (G). These hooks (D-G) may be configured for mating with a primary lock arm (H) housed within a fixed structure (I) of the thrust reverser (A). The primary lock arm (H) may have an upper primary lock arm receiver (J) and a lower primary lock arm receiver (K) at either end for receiving one of the upper door hooks (D,E) and one of two lower door hooks (F,G). A primary lock arm actuator (L) may pivot the lock arm (H) about a center pivot (M) such that the hooks (D-G) may be released from the lock arm (H), thereby unlocking the pivot doors (B,C). However, notice in FIG. 3 that each hook (D-G) may also comprise a hook safety tab (N), which may prevent the hook (D-G) or the receiver (J,K) from inadvertently sliding out of place. Therefore, in order for the primary lock arm (H) to release the upper door and lower door hooks (D-G), the door (B,C) must be slightly “overstowed” during opening and again during closing. Overstowing a pivot door (B,C) involves closing it slightly farther than a typical closed position, and then allowing the door (B,C) to move back into its typical closed position once the primary lock arm (H) is actuated to the desired orientation.
In addition to the two locks provided by the upper door hooks (D,E) and the lower door hooks (F,G), a third lock (not shown), referred to as a tertiary lock, may be used. The tertiary lock for each of the doors (B,C) are positioned in a center location on each door (B,C) with respect to the corresponding upper door hooks (D,E) and the corresponding lower door hooks (F,G). Tertiary locks are generally mechanically complex and may also be subject to a large amount of load if the primary and/or secondary locks fail.